But where will it appear? It is 5% towards the boost when the building is active? Meaning 400 -> 420 ?? If yes, why the building still shows the boost only 400 even though the upgrade is bought.

Or is it 5% towards my worker's number, so it boosts any of my workers who have at least 1 point in Magic or Rune Writing, or both, by 5% ?? Hence if my worker has 100 points in Magic, when the upgrade is bought it should jump to 105 !!

The same applies to all the building. I don't see the production of a certain resource to increase when the upgrade is bought. It should CLEARLY show somewhere how many Resources/points or power you are working with at a given moment.

With heroes it is easy, you see CLEARLY that when their building is active their POWER RISES by appropriate number and they are BLUE color coded. No such color coding or CLEAR indication of boost for Resources or Workers.

One dares to even question if the extra points or resources are even counted in.